An orthogonal frequency division multiplexing (hereinafter referred to as “OFDM”) method is a communication method that divides high-speed serial data into low-speed parallel signals, modulates the parallel signals into orthogonal subcarriers, and transmits the subcarriers.
Further, an orthogonal frequency-division multiple access (referred to as “OFDMA” or “OFDM-FDMA”) method is one of multiple access methods. The OFDMA method allocates a part of a resource to each of a plurality of layers in a two-dimensional map where a limited uplink/downlink radio resource is divided by a time axis and a frequency axis, and designs one layer at the corresponding part of the resource. In this case, the layer may be represented by the product of the number of users and the number of the transmission antennas when a plurality of users use a plurality of transmission antennas, respectively.
Meanwhile, channel estimation using a pilot may be used to compensate the distortion of the amplitude and phase of a symbol, which is caused by multipath attenuation of a radio channel. In this case, the pilot means a signal having structure or form, which is engaged between a transmitting terminal and a receiving terminal. The above-mentioned pilot is allocated to some subcarriers of a tile that are a basic unit of the radio resource allocation, and the receiving terminal can estimate the channel value of the corresponding channel by a pilot.
However, since a method of determining which channel the corresponding pilot corresponds to varies depending on a method of designing a pilot on a tile, transmission efficiency and channel estimation performance vary. For this reason, an efficient pilot design method is required.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.